Syntax Error When Loading Lua Script

Im trying to use lua in my application, but when trying to load a script using lua_loadBuffer, I get an error message.

LuaContext := lua_newstate(@Alloc, nil);
  try
    luaL_openlibs(LuaContext);
    s := 'print("hi")';
    lua_register(LuaContext, 'print', @print_func);  
    if luaL_loadbuffer(LuaContext, PChar(s), Length(s), PChar('sample1')) <> 0 then
    begin
      raise Exception.Create(lua_tostring(LuaContext, -1));  //<- I get the following error message here:  [string "sample1"]:1: syntax error
    end;
    if lua_pcall(LuaContext, 0, 0, 0) <> 0 then
      Exception.Create('');
  except
      Debugln('Error: ' + lua_tostring(LuaContext, -1));
  end;

Afaik the lua code is valid, right? Just a "syntax error" isn't very descriptive, and me not having any expierience with the lua, I don't even know where to look for mistakes.